my payment card has expired how can I update my details

Log into your account in the App Store/iTunes and you should be able to change/verify it there. Or you can click the blue Edit payment methods in the article below. When signed in and the page loads, you will be on the credit card page. If you have a subscription, you need to add the new card, and then promote it to the primary payment method before you can remove the old card.

Apple ID payment information - change.  *